Process for extracting water-soluble substances from raw fibrous materials containing the same, and for simultaneously forming the fibrous materials into a web, and system of apparatus therefor



June 7, 19321 R MURDOCK 1,861,933 PROCESS FOR EXTRACTING WATER SOLUBLE SUBSTANCES FROM RAW FIBROUS MATERIALS CONTAINING THE SAME, AND FOR SIMULTANEOUSLY FORMING THE FIBROUS MATERIALS INTO A WEB, AND SYSTEM OF APPARATUSTHEREFOR Filed Sept. 26, 1950 75,0 lifer a ;i PROQESS FOR EXTRACTING WATER-SOLUBLE SUBSTANCES FROM RAW FIBROUS MATE- Patented June ,7, 1932 UNITED STATES PATENT orrl'ca HAROLD RMURDOCK, OF CANTON, NORTH OAEOLINA, ,ASSIGNOB TO THE OHAITIOIT FTBRE COMJPANY, OF CANTON, NORTHVCAROLINA, A CORPO ZRATION'OF OHIO BIALS ING THE SAME, AN FOR SIMULTANEOUSLY FORMING THE FIBROUS MATERIALS INTO A WEB,- AND SYSTEM APPARATUS THEREFOR Application filed September 26,,1930.' Serial No. 484,688.

This invention relates to processes for extracting water-soluble substances from fibrous materials containing the same, and is concerned with an interrelated process for extracting water-soluble constituents and forming a fibrous web from fibrous paperpulp-yielding materials and. with a system of apparatus adapted to the carrying out of the said process. l

More particularly, this invention finds application to an extraction treatment of a fibrous material, such, for instance, as the woody part of the oak, hemlock or chestnut, containing water soluble constituents adapted for use as tanning agents, or of the larch,

whose water-soluble constituents contain chanical means to a c'omminuted state, and

the comminuted material is extracted by being broughtinto contact with water on the principle of-counter-current flow. In order to secure, in a reasonable length of time, ,an adequate degree of removal of the watersoluble substances present in the fibrous ma- .terials, it has been considered necessary to bring the materials to a relatively fine state of comminution. It has been the practice to maintain the extractant at any suitable temperature favorable to the production of an extract of a desired degree of purity. In those cases where the extractant was maintained at a temperature at or above 212 F.,

the extraction was effected in pressure containers; at working temperatures below 212 7 F., open tanks or tubs were employed. This fine subdivision ofthe fibrous materials in their natural, relatively dry, state resulted in the production of a product containing a large proportion of powdered material and of fibrous articles in which the ultimate fibers and ber bundles were greatly shortened, with the result that, after extraction,

the by-product fibrous materials no longer had, value as "raw materials for paper pulp. According to one process-by which the fibers .7 are preserved more nearly in thenatural length, the materials are chipped or cut so that they are, for example, passed through a one inch screen and are retained on a one quarterinch screen. It has been found that by using chips of this size the resulting pulp possesses reasonably cod fiber, but the process of extraction 0 the water-soluble constituents is made nece'ssarily difiicult and requires the use of pressure autoclaves with water at high temperature.

This forced extraction produces a dark colored extract and involves considerable labor, equipment and difiiculties in operation. c t

Anv object." of the present invention is to provide a. process by which to obtain relatively lighter colored extracts while preserving the fibrous nature of the raw materials and the relative lengthof the natural fibers, An-

other object of the invention isto provide an extraction and pulping process by which to obtain a desirable extract and a desirable paper-forming pulp, which process involves no diflicult operations or complicated and expensive equipment and requires but little labor. A further object of the invention is to provide a system of apparatus adapted for use in such: a process. I

The crux of the present invention may be said to reside in fibrilating the raw fibrous material containing water-soluble extractives in a grinding operation in the presence of aqueous liquid, extracting from the resulting pulpy mass Water-soluble substances contained therein, and forming the pulp freed of Water-soluble substances into a web.

The first step of my process consists in fibrilating the raw fibrous material (e. wood) containing valuable Water-soluble su stances by a grinding operation. This 0 eration may be effected in an apparatus suc as is used commonly in the preparation of ground wood pulp. This apparatus-usually comprises a rotatlng stone n which are cut grooves to act as cutting surfaces and imbed the fibers after they are out from the material being fibrilated. The fibrous materials are held in position on the rotating stone by one or more devices comprising a pocket or compartment and a pressure-supplying plunger for forcing the raw material against the stone to produce fibrilation. The rotating stone is partially immersed in a trough filled with water so that the fibers are washed from the grooves in the-stone and retained in the trough. Showers are also directed on the stone to further clear the cutting surfaces. Due to the heat of grinding, it is possible to maintain an elevated temperature in the trough by regulating the amount of shower water used on the stone. In the trough the extraction process becomes active. The pulpy mass thus prduced is moved through the trough by means of the rotating stone, and overflows from one end of the trough intoa pit or reservoir due temperature for a sufiicient length of time to to the continued additions of water and fibrous materials on the cutting surfaces of the stone.

Should satisfactory extraction of the water-soluble ingredients not be effected by the time the fibrous materials enter the pit it is sometimes necessary to use a stock chest, whereby the fibers are maintained in direct contact with water at a more or less elevated obtain satisfactory removal of the water-soluble ingredients. The pulpy mass comprising pulp fiber and valuable water-soluble extract, which overflows from the trough, or the contents of the pit and stock chest (if used), may be screened in order to remove the coarser fibers from the pulp.

The slushed pulp is then conveyed with the water-soluble extract to a web-forming device, such as a thickener, in order to separate the pulp from the water-soluble extract. At this point the pulp leaves its initial extracting medium, passing, preferably, to a diffusing battery where it is washed countercurrently by the well known principle in order to effectively obtain the water-soluble extractive materials which have been made readily available by the previously mentioned ulping operation. The water solution commg from the thickener, which solution contains valuable water-soluble ingredients of the fibrous materials, may be returned to the grinder for reuse. It may likewise be used to dilute the slushed pulp coming from the grinder where it enters the pit or in the stock chest or at the screen, or it may be diverted to a suitable evaporating device if and when sufliciently concentrated as to its content of dissolved solids.

The pulp, which comes from the thickener in the form of a web, may be used as such for many purposes, so that a cylinder, or Fourdrinier, paper makin machine may be used effectively as the thi ening device. Where this is contemplated I may, and preferably do, add to the pulp moving to the paper machine a suitable amount, say or more, of a suspension of longer-fibered pulp, such for instance as that produced by a chemical pulping process, whereby to alter or modify the characteristics of the resulting web, e. g., to

second thickener for make-up water in the a grinding operation.

It should be apparent from the above that the described extraction system is cyclic and continuous, since the relatively concentrated extractant, hereinafter called strong liquor, may be removed from the system as desired and used as such or evaporated to a more concentrated product.

Thus the relatively concentrated extract ant, or washings, may be bled (continuously or intermittently) to the evaporators, and condensate fromthetevaporators may be returned to the cyclic system at any desired point,for instance, to the diffusing operation, to the grinding operation, as diluent of the freshly ground pulpy mass, or wherever else in the series of operations it may be found desirable to introduce water.

This process for extractin water-soluble materials is found to yield e ciently a much better and lighter colored product than that which it has been possible to obtain by the older methods. This is a decided advantage,

especially in those cases where the extractive materials are tanning agents. It has been found quite im ossible to obtain a light color when tanning ides due to the coloring ingredients present in the vegetable tanning solution obtained by such extraction, unless such tanning materials were treated previously to remove the deleterious coloring materials.

By my process an extractant is obtained which makes further treatment unnecessary in the obtaining of an extract adapted for use in the production of light colored tanned hides.

In the grinding of pulp by what is commonly known as the ground wood method a great deal of ener y is dissipated in the form of heat which, so ar as I am aware, has never 7 been utilized satisfactorily. It should be apparent that the present process utilizes the heat to a decided advantage," the heat assisting decidedly in the rate of removal of the water-soluble ingredients.

lates through the system in cyclic manner will be found suitable for evaporation when its total solid content is around 2%, but in some cases it will be found desirable to maintain a concentration of total solids in the circulating system of extraction higher than. 2%. The ratio of fibrous material to extractant depends entirely on the nature of the fiber and water-soluble constituent desired. The usual relationship used in ground wood products will be found satisfactory in practice of this process.

In order that the invention may be better understood, reference is made to the accompanying drawing, which is a diagrammatic representation of a system of apparatus for carrying out the above-described process.

In the drawing 1 represents a wood grinding machine of conventional design, including a trough 1a; 2 represents a pit, and 3 a stockchest, for the reception of pulpy mass from grinder 1; 4 is a screening device for the separation from the pulpy mass of slivers knots, and coarser fiber bundles; 5 is a thickening device, of conventional design, for the reduction of the liquid content of a pulpy mass; 6 diagrammatically represents a battery of difl'users or counter-current washers; 7 is a thickening device which may and preferably does take the form of a papermaking machine such as a cylinder machine or Fourdrinier machine; and 8 represents an evaporator. By means of a suitable system of piping aqueous liquid maybe supplied to grinder 1, pit 2, stock chest 3, or screens 4, either from an outside source of aqueous liquid or from thickeners 5 and 7 ordifi'users 6. Likewise, the extractant may be diverted to evaporator 8 from thickeners 5 or 7 or diffusers 6.

While in the foregoing the device for fibrilating the raw fibrous material has been described as being a wood grinding machine of conventional design, it is not my intention to exclude the use of other equivalent means for grinding wood to obtain a fibrous pulp. Thus, for instance, I may with like results make use of a device wherein wood chips are fibrilated between rotating discs. or of any other means similar to that illustratively described hereinbefore.

In carrying out the operations of the process using the above-described. apparatus, the fibrous materials, such as wood, are fed into the pockets of the grinder (1), where they are fibrilated by means of the rotating stone, in the presence of aqueous extractant, and in company with the water solution they fall into the trough (10), directly belowthe grinder proper and then, after an interval, the pulp, in a comparatively high consistency, overflows into the pit (2). At this point the pulpy mass may be diluted to a lower consistency and passed on to the stock chest (3). This stock chest may or may not be used, depending upon the efliciency and ease of removal of the water-soluble ingredients in the initial grinding operation. The stock chest is preferably capable of maintaining an elevated temperature to assist the extraction process. The pulp and its water extractant is then passed onto screens (4), whereby the coarser fibers are removed and the isolated finer fibers in their medium of water extractant are passed to a thickener (5) The water extractant at this pointis returned to the grinding operation, or used in dilution at the pit, stock chest or screens. When the solution becomes concentrated enough it may be continuously withdrawn, as is shown in the diagram, as strong liquor for evaporation. Condensate from the evaporators may be returned to the cycle at any point where addition of fresh water has been indicated. The pulppassing from the thickener (5), is conveyed to a diffuser (6), whereby it is washed with water counter-currently and freed of water-soluble constituents. The

washings from the difiusing operation may be used as makeup water in the grinding operation, or elsewhere as may be found practical, in order to recover the valuable ingredients which they contain. The pulp coming from the difi'users is passed to a thickener 3 substances from raw fibrous material containing the sameand for simultaneously preparing said material in the form of a paper web, which includes the following steps: (a) grinding the raw fibrous material in the presence of aqueous liquid, (72) subjecting the L resulting fibrilated material to prolonged contact with said aqueous liquid whereby to promote solution in the liquid of the watersoluble substances contained in the material,

(0) at least partially separating the result- 1- 1.

using a portion of the retained aqueous solution from the steps (0) and (e) as aqueous liquid in one of the steps (a) and (b) and from the remaining portion of the retained aqueous solution from steps (a) and (d) separating water whereby to yield a concentrated extract of the aforesaid water-soluble substances, and (9) using the water separated in step (f) as at least a part of the aqueous liquid in one of the steps (b) and (d).

2. A system of apparatus for extracting water-soluble substances from raw fibrous materials containing the same and for simultaneously preparing the fibrous material in the form of a web, which comprises, in cooperation, means for fibrilating raw fibrous material in the presence of aqueous liquid whereby to yield a pulpy mass of the material, means for holding fibrilated material in prov longed contact with aqueous liquid, means for delivering pulpy mass from the aforesaid fibrilating means to said contacting means, means for separating aqueous liquid from fibrilated material, means for delivering pulpy mass from said contacting means to said separating means, a second means for holding fibrilated material in prolonged contact with aqueous liquid as a pulpy mass, means for delivering separated fibrilated material from the aforesaid separating means to said second contacting means and means for delivering aqueous liquid to the latter, means for separating fibrilated material from aqueous liquid and simultaneously forming the fibrilated material into a web, means for delivering pulpy mass from said second contacting means to said separating and webforming means, an evaporator, means for delivering aqueous liquid from at least one of said separating means to said evaporator and for delivering condensate from said evaporator to at least one of the following: the fibrilating means, the separating means, and the second contacting means.

In testimony whereof, I afiix my signature.

HAROLD R. MURDOCK. 

